Electron emission device and display device using the same

ABSTRACT

An electron emission device exhibits a high electron emission efficiency. The device includes an electron supply layer of metal or semiconductor, an insulator layer formed on the electron supply layer, and a thin-film metal electrode formed on the insulator layer. The insulator layer is made of an amorphous dielectric substance and has a film thickness of 50 nm or greater and has an amorphous phase with an average grain size of 5 to 100 nm as a major component and a polycrystal phase as a minor component. When an electric field is applied between the electron supply layer and the thin-film metal electrode, the electron emission device emits electrons.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electron emission device and anelectron emission display device using the same.

2. Description of the Related Art

In field electron emission display apparatuses, an FED (Field EmissionDisplay) is known as a planar emission display device equipped with anarray of cold-cathode electron emission source which does not requirecathode heating. The emission principle of, for example, an FED using aspindt type cold cathode is as follows: Its emission principle is like aCRT (Cathode Ray Tube), although this FED has a cathode array differentfrom that of CRT, that is, electrons are drawn into a vacuum space bymeans of a gate electrode spaced apart from the cathode, and theelectrons are made to impinge upon the fluorescent substance that iscoated on a transparent anode, thereby causing light emission.

This field emission source, however, faces a problem of low productionyield because the manufacture of the minute spindt type cold cathode iscomplex and involves many steps.

There also exists an electron emission device with ametal-insulator-metal (MIM) structure as a planar electron source. Thiselectron emission device with an MIM structure has an Al layer as acathode, an Al₂ O₃ insulator layer of about 10 nm in film thickness andan Au layer, as an anode, of about 10 nm in film thickness formed inorder on the substrate. With this device placed under an opposingelectrode in a vacuum, when a voltage is applied between the underlyingAl layer and the overlying Au layer and an acceleration voltage isapplied to the opposing electrode, some of electrons leap out of theoverlying Au layer and reach the opposing electrode. Even the electronemission device with the MIM structure does not yet provide a sufficientamount of emitted electrons.

To improve this property of emission, it is considered that there is anecessity to make the Al₂ O₃ insulator layer thinner by about severalnanometers and make the quality of the membranous of the Al₂ O₃insulator layer and the interface between the Al₂ O₃ insulator layer andthe overlying Au layer more uniform.

To provide a thinner and more uniform insulator layer, for example, anattempt has been made to control the formation current by using ananodization thereby to improve the electron emission characteristic, asin the invention described in Japanese Patent Application kokai No. Hei7-65710.

However, even an electron emission device with an MIM structure which ismanufactured by this method ensures an emission current of about 1×10⁻⁵A/cm² and an electron emission efficiency of about 1×10⁻³.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anelectron emission device with a high electron emission efficiency and anelectron emission display apparatus using the same.

An electron emission device according to the invention comprises:

an electron supply layer of metal or semiconductor;

an insulator layer formed on the electron supply layer; and

a thin-film metal electrode formed on the insulator layer and facing avacuum space,

whereby the electron emission device emits electrons when an electricfield is applied between the electron supply layer and the thin-filmmetal electrode,

characterized in that said insulator layer is made of an amorphousdielectric substance and has a film thickness of 50 nm or greater andhas an amorphous phase with an average grain size of 5 to 100 nm as amajor component and a polycrystal phase as a minor component, wherebythe electron emission device emits electrons when an electric field isapplied between the electron supply layer and the thin-film metalelectrode.

According to the electron emission device of the invention with theabove structure, through-bores are not likely to be produced in theinsulator layer because of its large thickness and then the productionyield is improved. The emission current of the electron emission deviceis greater than 1×10⁻⁶ A/cm² and is approximately 1×10⁻³ A/cm², and theelectron emission efficiency obtained is 1×10⁻¹. Therefore, thiselectron emission device, when in use in a display device, can provide ahigh luminance, can suppress the consumption of the drive current andthe generation of heat from the device, and can reduce a burden on thedriving circuit.

The electron emission device of the invention is a planar or spot-likeelectron emission diode and can be adapted to high speed devices such asa source of a pixel vacuum tube or bulb, an electromagnetic emissionsource of an electron microscope, a vacuum-micro electronics device andthe like. In addition, this electron emission device can serve as alight-emitting diode or a laser diode which emits electromagnetic wavesof infrared rays, visible light or ultraviolet rays.

Moreover a display device using an electron emission device according tothe invention comprises:

a pair of first and second substrates facing each other with a vacuumspace in between;

a plurality of electron emission devices provided on the firstsubstrate;

a collector electrode provided in the second substrate; and

a fluorescent layer formed on the collector electrode;

each of the electron emission devices comprising an electron supplylayer of metal or semiconductor; an insulator layer formed on theelectron supply layer; and a thin-film metal electrode formed on theinsulator layer and facing a vacuum space, wherein said insulator layeris made of an amorphous dielectric substance and has a film thickness of50 nm or greater and has an amorphous phase with an average grain sizeof 5 to 100 nm as a major component and a polycrystal phase as a minorcomponent.

In addition, a display device using an electron emission deviceaccording to the invention comprises:

a pair of a device substrate and a transparent substrate facing eachother with a vacuum space in between;

a plurality of ohmic electrodes formed in parallel on an inner surfaceof the device substrate;

a plurality of electron emission devices provided on the ohmicelectrodes, each of the electron emission devices comprising an electronsupply layer of metal or semiconductor; an insulator layer formed on theelectron supply layer; and a thin-film metal electrode formed on theinsulator layer and facing the vacuum space, wherein said insulatorlayer is made of an amorphous dielectric substance and has a filmthickness of 50 nm or greater and has an amorphous phase with an averagegrain size of 5 to 100 nm as a major component and a polycrystal phaseas a minor component;

a plurality of bus electrodes formed on parts of the thin-film metalelectrodes and extending in parallel to one another and perpendicular tothe ohmic electrodes so as to electrically connect adjoining thin-filmmetal electrodes;

a plurality of collector electrodes provided in the transparentsubstrate; and

fluorescent layers formed on the collector electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an electron emissiondevice according to the invention;

FIG. 2 is a graph showing a dependency of the electron emission currenton the film thickness of an SiO₂ layer in the electron emission deviceembodying the invention;

FIG. 3 is a graph showing a dependency of the electron emissionefficiency on the film thickness of the SiO₂ layer in the electronemission device embodying the invention;

FIG. 4 is a graph illustrating a dependency of the electron emissioncurrent on the grain size of an SiO₂ layer in the electron emissiondevice according to the invention;

FIG. 5 is graph showing a dependency of the electron emission efficiencyon the grain size of the SiO₂ layer in the electron emission deviceaccording to the invention;

FIG. 6 is a schematic perspective view showing an electron emissiondisplay device according to one embodiment of the invention; and

FIG. 7 is a diagram for explaining the operation of the electronemission device of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will bedescribed in more detail with reference to the accompanying drawings.

As shown in FIG. 1, an electron emission device embodying the inventionhas an ohmic electrode 11 formed on a device substrate 10. The electronemission device further has an electron supply layer 12 of metal orsemiconductor such as Si, an insulator layer 13 of SiO₂ or the like anda thin-film metal electrode 15 of metal facing a vacuum space which arelayered or formed in turn on the ohmic electrode. The electron emissiondevice emits electrons when an electric field is applied between theelectron supply layer and the thin-film metal electrode. The insulatorlayer 13 is made of a dielectric substance and has a very large filmthickness of 50 nm or greater. The electron emission device can beregarded as a diode of which the thin-film metal electrode 15 at itssurface is connected to a positive potential Vd and the back i.e., ohmicelectrode 11 is connected to a ground potential. When the voltage Vd isapplied between the ohmic electrode 11 and the thin-film metal electrode15 to supply electrons into the electron supply layer 12, a diodecurrent Id flows. Since the insulator layer 13 has a high resistance,most of the applied electric field is applied to the insulator layer 13.The electrons travel inside the insulator layer 13 toward the thin-filmmetal electrode 15. Some of the electrons that reach near the thin-filmmetal electrode 15 tunnel through the thin-film metal electrode 15, dueto the strong field, to be discharged out into the vacuum space. Theelectrons e (emission current Ie) discharged from the thin-film metalelectrode 15 by the tunnel effect are accelerated by a high voltage Vc,which is applied to an opposing collector electrode (transparentelectrode) 2, and is collected at the collector electrode 2. If afluorescent substance is coated on the collector electrode 2,corresponding visible light is emitted.

While Si is particularly effective as a material for the electron supplylayer of the electron emission device, an elemental semiconductor or acompound semiconductor of an element of a group IV, a group III-V, agroup II-VI or the like, such as a germanium (Ge), silicon carbide(SiC), gallium arsenide (GaAs), indium phosphide (InP), or cadmiumselenide (CdSe) can be used as well.

While metals such as Al, Au, Ag and Cu are effective as the electronsupplying material, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Y, Zr, Nb,Mo, Tc, Ru, Rh, Pd, Cd, Ln, Sn, Ta, W, Re, Os, Ir, Pt, Tl, Pb, La, Ce,Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like can beused as well.

Silicon oxide SiO_(x) (wherein subscribed x represents an atomic ratio)is effective as the dielectric material of the insulator layer and,metal oxides or metal nitrides such as LiO_(x), LiN_(x), NaO_(x),KO_(x), RbO_(x), CsO_(x), BeO_(x), MgO_(x), MgN_(x), CaO_(x), CaN_(x),SrO_(x), BaO_(x), ScO_(x), YO_(x), YN_(x), LaO_(x), LaN_(x), CeO_(x),PrO_(x), NdO_(x), SmO_(x), EuO_(x), GdO_(x), TbO_(x), DyO_(x), HoO_(x),ErO_(x), TmO_(x), YbO_(x), LuO_(x), TiO_(x), TiN_(x), ZrO_(x), ZrN_(x),HfO_(x), HfN_(x), ThO_(x), VO_(x), VN_(x), NbO_(x), TaO_(x), TaN_(x),CrO_(x), CrN_(x), MoO_(x), MoN_(x), WO_(x), WN_(x), MnO_(x), ReO_(x),FeO_(x), FeN_(x), RuO_(x), OsO_(x), CoO_(x), RhO_(x), IrO_(x), NiO_(x),PdO_(x), PtO_(x), CuO_(x), CuN_(x), AgO_(x), AuO_(x), ZnO_(x), CdO_(x),HgO_(x), BO_(x), BN_(x), AlO_(x), AlN_(x), GaO_(x), GaN_(x), InO_(x),TiO_(x), TiN_(x), SiN_(x), GeO_(x), SnO_(x), PbO_(x), PO_(x), PN_(x),AsO_(x), SbO_(x), SeO_(x), TeO_(x) and the like can be used as well.Furthermore, metal complex oxides such LiAlO₂, Li₂ SiO₃, Li₂ TiO₃, Na₂Al₂₂ O₃₄, NaFeO₂, Na₄ SiO₄, K₂ SiO₃, K₂ TiO₃, K₂ WO₄, Rb₂ CrO₄, Cs₂CrO₄, MgAl₂ O₄, MgFe₂ O₄, MgTiO₃, CaTiO₃, CaWO₄, CaZrO₃, SrFe₁₂ O₁₉,SrTiO₃, SrZrO₃, BaAl₂ O₄, BaFe₁₂ O₁₉, BaTiO₃, Y₃ Al₅ O₁₂, Y₃ Fe₅ O₁₂,LaFeO₃, La₃ Fe₅ O₁₂, La₂ Ti₂ O₇, CeSnO₄, CeTiO_(x), Sm₃ Fe₅ O₁₂, EuFeO₃,Eu₃ Fe₅ O₁₂, GdFeO₃, Gd₃ Fe₅ O₁₂, DyFeO₃, Dy₃ Fe₅ O₁₂, HoFeO₃, Ho₃ Fe₅O₁₂, ErFeO₃, Er₃ Fe₅ O₁₂, Tm₃ Fe₅ O₁₂, LuFeO₃, Lu₃ Fe₅ O₁₂, NiTiO₃, Al₂TiO₃, FeTiO₃, BaZrO₃, LiZrO₃, MgZrO₃, HfTiO₄, NH₄ VO₃, AgVO₃, LiVO₃,BaNb₂ O₆, NaNbO₃, SrNb₂ O₆, KTaO₃, NaTaO₃, SrTa₂ O₆, CuCr₂ O₄, Ag₂ CrO₄,BaCrO₄, K₂ MoO₄, Na₂ MoO₄, NiMoO₄, BaWO₄, Na₂ WO₄, SrWO₄, MnCr₂ O₄,MnFe₂ O₄, MnTiO₃, MnWO₄, CoFe₂ O₄, ZnFe₂ O₄, FeWO₄, CoMoO₄, CoTiO₃,CoWO₄, NiFe₂ O₄, NiWO₄, CuFe₂ O₄, CuMoO₄, CuTiO₃, CuWO₄, Ag₂ MoO₄, Ag₂WO₄, ZnAl₂ O₄, ZnMoO₄, ZnWO₄, CdSnO₃, CdTiO₃, CdMoO₄, CdWO₄, NaAlO₂,MgAl₂ O₄, SrAl₂ O₄, Gd₃ Ga₅ O₁₂, InFeO₃, MgIn₂ O₄, Al₂ TiO₅, FeTiO₃,MgTiO₃, NaSiO₃, CaSiO₃, ZrSiO₄, K₂ GeO₃, Li₂ GeO₃, Na₂ GeO₃, Bi₂ Sn₃ O₉,MgSnO₃, SrSnO₃, PbSiO₃, PbMoO₄, PbTiO₃, SnO₂ --Sb₂ O₃, CuSeO₄, Na₂ SeO₃,ZnSeO₃, K₂ TeO₃, K₂ TeO₄, Na₂ TeO₃, Na₂ TeO₄ and the like can be used aswell and still furthermore, sulfides such as FeS, Al₂ S₃, MgS, ZnS andthe like, fluorides such as LiF, MgF₂, SmF₃ and the like, chlorides suchas HgCl, FeCl₂, CrCl₃ and the like, bromides such as AgBr, CuBr, MnBr₂and the like, iodide such as PbI₂, CuI, FeI₂ and the like and metaloxidized nitrides such as SiAlON and the like can be used as well forthe insulator layer.

Moreover, carbon such as diamond, Fulleren (C_(2n)) and the like ormetal carbide such as Al₄ C₃, B₄ C, CaC₂, Cr₃ C₂, MO₂ C, MOC, NbC, SiC,TaC, TiC, VC, W₂ C, WC, ZrC and the like are also effective as thedielectric material of the insulator layer. Fulleren (C_(2n)) consistsof carbon atoms. The representative C₆₀ is a spherical surface basketmolecule as known a soccer ball molecule. There is also known C₃₂ toC₉₆₀ and the like. The subscribed x in O_(x), N_(x) and the like in theabove chemical formulas represent atomic ratios and also herein after.

Although metals such as Pt, Au, W, Ru and Ir are effective as thematerial for the thin-film metal electrode 15 on the electron emissionside, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Tc,Rh, Pd, Ag, Cd, Ln, Sn, Ta, Re, Os, Tl, Pb, La, Ce, Pr, Nd, Pm, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like can be used as well.

The material for the device substrate 10 may be ceramics such as Al₂ O₃,Si₃ N₄ or BN instead of glass.

Although sputtering is particularly effective in forming those layersand the substrate, vacuum deposition method, CVD (Chemical VaporDeposition), laser aberration method, MBE (Molecular Beam Epitaxy) andion beam sputtering are also effective.

EXAMPLES

Electron emission devices according to the invention were fabricated andtheir characteristics were examined specifically.

An electron supply layer of silicon (Si) was formed at 5000 nm thick, bysputtering, on an electrode surface of a device substrate 10 of glass onwhich an Al ohmic electrode was formed 300 nm thick by sputtering. Aplurality of Si substrates of this type were prepared.

Then, SiO₂ insulator layers were formed on the electron supply layers ofthe Si substrate by sputtering respectively while changing the filmthickness of the insulator layer in a range from 0 nm to 500 nm. Thus aplurality of SiO₂ insulator substrates were provided. The SiO₂ insulatorlayer was formed by sputtering by using a gas of Ar, Kr or Xe or amixture thereof, or a gas mixture essentially consisting of one of thoserare gases with O₂, N₂, H₂ or the like mixed therein, under thesputtering conditions of a gas pressure of 0.1 to 100 mTorr, preferably0.1 to 20 mTorr and the forming rate of 0.1 to 1000 nm/min, preferably0.5 to 100 nm/min. The single layer or multilayer structure, theamorphous or crystal phase, the grain size and the atomic ratio of theinsulator layer 13 was able to be controlled by properly altering thesputtering target and sputtering conditions of the sputtering device.

The analysis on the SiO₂ insulator layer in this embodiment by X-raydiffraction was performed and then the result showed some diffractionintensity Ic caused by the crystal portion and some halo intensity Iacaused by the amorphous phase at a ratio Ic/Ia of about 5/95. It can beassumed from this result that SiO₂ of the insulator layer consists of adispersed crystal portion of 5% and an amorphous phase portion of 95%.

Finally, a thin-film metal electrode of Pt was formed 10 nm thick on thesurface of the amorphous SiO₂ layer of each substrate by sputtering,thus providing a plurality of device substrates.

Meanwhile, transparent substrates were prepared, each of which has anITO collector electrode formed inside a transparent glass substrate andhas a fluorescent layer of a fluorescent substance corresponding to R, Gor B color emission formed on the collector electrode by the normalscheme.

Electron emission devices were assembled in each of which the devicesubstrate and the transparent substrate are supported apart from oneanother by 10 mm in parallel by a spacer in such a way that thethin-film metal electrode 15 faced the collector electrode 2, with theclearance therebetween made to a vacuum of 10⁻⁷ Torr or 10⁻⁵ Pa.

Then, the diode current Id and the emission current Ie corresponding tothe thickness of the SiO₂ film of each of the acquired plural deviceswere measured.

FIGS. 2 and 3 show the relationships between the film thickness of eachSiO₂ layer and the maximum emission current Ie, and between the filmthickness and the maximum electron emission efficiency (Ie/Id) for eachfilm thickness respectively when a voltage Vd of 0 to 200 V was appliedto the prepared electron emission devices. As apparent from FIGS. 2 and3, while the emission current and the electron emission efficiency weresaturated from the thickness of 50 nm, the devices whose SiO₂ layers hadthicknesses of 300 to 400 nm showed the maximum emission current ofabout 1×10⁻³ A/cm² and the maximum electron emission efficiency of about1×10⁻¹.

It is understood from those results that by applying a voltage of 200 Vor lower, the emission current of 1×10⁻⁶ A/cm² or greater and theelectron emission efficiency of 1×10⁻³ or greater can be acquired froman electron emission device which has an SiO₂ dielectric layer 50 nm orgreater in thickness, preferably 100 to 400 nm in thickness.

With a voltage of approximately 4 kV applied between thefluorescent-substance coated collector electrode and the thin-film metalelectrode, a uniform fluorescent pattern corresponding to the shape ofthe thin-film metal electrode was observed in the devices whose SiO₂layers have thicknesses of 50 nm or greater. This shows that theelectron emission from the amorphous SiO₂ layer is uniform and has ahigh linearity, and that those devices can serve as an electron emissiondiode, or a light-emitting diode or laser diode which emitselectromagnetic waves of infrared rays, visible light or ultravioletrays.

Next, there were measured the diode current Id and the emission currentIe corresponding to the grain size of SiO₂ with respect the insulatorlayers each having a 400 nm thickness of the resultant devices.

FIGS. 4 and 5 show the relationships between the grain size of SiO₂layer and both the maximum emission current Ie and the maximum electronemission efficiency (Ie/Id) respectively. As seen from FIGS. 4 and 5,the distribution of grain size in amorphous SiO₂ exists. It isunderstood from those results that the emission current of 1×10⁻⁶ A/cm²or greater and the electron emission efficiency of 1×10⁻³ or greater canbe acquired from an electron emission device which has an insulatorlayer of amorphous SiO₂ having a average grain size of 5 to 100 nm.

When there were observation of the surface of the insulator layer by ascanning electron microscope (SEM) during the above formation process,grain surface each having an about 20 nm diameter appeared in comparisonwith that formed by CVD.

The peculiar phenomenon that the tunnel current flows through theinsulator layer which has a thickness of 50 nm or greater seems to beoriginated from the grain structure of SiO₂ of the insulator layer. Asshown in FIG. 7, while SiO₂ is an insulator by nature, multiple bandswith low potentials are caused by the grain structure or crystal defectsadjacent thereto or impurities in the insulator layer. It is assumedthat electrons tunnel through one low-potential band after another, andthus tunnel through the insulator layer of 50 nm or greater in thicknessas a consequence.

FIG. 6 shows an electron emission display device according to oneembodiment of the invention. This embodiment comprises a pair of thetransparent substrate 1 and the device substrate 10, which face eachother with a vacuum space 4 in between. In the illustrated electronemission display apparatus, a plurality of transparent collectorelectrodes 2 of, for example, an indium tin oxide (so-called ITO), tinoxide (SnO), zinc oxide (ZnO) or the like, are formed in parallel on theinner surface of the transparent glass substrate 1 or the displaysurface (which faces the back substrate 10). The collector electrodes 2may be formed integrally. The transparent collector electrodes whichtrap emitted electrons are arranged in groups of three in associationwith red (R), green (G) and blue (B) color signals in order to provide acolor display panel, and voltages are applied to those three collectorelectrodes respectively. Therefore, fluorescent layers 3R, 3G and 3B offluorescent substances corresponding to R, G and B are respectivelyformed on the three collector electrodes 2 in such a way as to face thevacuum space 4.

A plurality of ohmic electrodes 11 are formed in parallel on the innersurface of the device substrate 10 of glass or the like which faces thetransparent glass substrate 1 with the vacuum space 4 in between (i.e.,said inner surface faces the transparent glass substrate 1) via anauxiliary insulator layer 18. The auxiliary insulator layer 18 iscomprised of an insulator such as SiO₂, SiN_(x), Al₂ O₃ or AlN, andserves to prevent an adverse influence of the device substrate 10 on thedevice (such as elution of an impurity such as an alkaline component ora roughened substrate surface). A plurality of electron emission devicesS are formed on the ohmic electrodes 11. In order to adjoining thin-filmmetal electrodes 15 are electrically connected to each other, aplurality of bus electrodes 16 are formed on parts of the thin-filmmetal electrodes 15, extending in parallel to one another andperpendicular to the ohmic electrodes 11. Each electron emission deviceS comprises the electron supply layer 12, the insulator layer 13 and thethin-film metal electrode 15 which are formed in order on the associatedohmic electrode 11. The thin-film metal electrodes 15 face the vacuumspace 4. A second auxiliary insulator layer 17 with openings is formedto separate the surfaces of the thin-film metal electrodes 15 into aplurality of electron emission regions. This second auxiliary insulatorlayer 17 covers the bus electrodes 16 to prevent unnecessaryshort-circuiting.

The material for the ohmic electrodes 11 is Au, Pt, Al, W or the likewhich is generally used for the wires of an IC, and has a uniformthickness for supplying substantially the same current to the individualdevices.

While silicon (Si) is one material for the electron supply layer 12, itis not restrictive for the electron supply layer of the invention andother semiconductors or metals of any of amorphous, polycrystal andmonocrystal can be used as well.

From the principle of electron emission, it is better that the materialfor the thin-film metal electrode 15 has a lower work function .oslashed. and is thinner. To increase the electron emission efficiency,the material for the thin-film metal electrode 15 should be a metal ofthe group I or group II in the periodic table; for example, Cs, Rb, Li,Sr, Mg, Ba, Ca and the like are effective and alloys of those elementsmay be used as well. To make the thin-film metal electrode 15 very thin,the material for the thin-film metal electrode 15 should be a chemicallystable metal with a high conductivity; for example, single substances ofAu, Pt, Lu, Ag and Cu or alloys thereof are desirable. It is effectiveto coat or dope a metal with a low work function as described above onor in those metals.

The material for the bus electrodes 16 can be Au, Pt, Al or the likewhich is generally used for the wires of an IC, and should have athickness enough to supply substantially the same potential to theindividual devices, adequately of 0.1 to 50 μm.

A simple matrix system or an active matrix system may be employed as thedriving system for the display device of the invention.

The electron emission device of the invention can be adapted to alight-emitting source for a pixel bulb, an electron emission source foran electron microscope and a fast device such as a vacuummicroelectronics device, and can serve as a planar or spot-like electronemission diode, a light-emitting diode or a laser diode which emitselectromagnetic waves of infrared rays, visible light or ultravioletrays.

What is claimed is:
 1. An electron emission device comprising:anelectron supply layer of metal or semiconductor; an insulator layerformed on the electron supply layer; and a thin-film metal electrodeformed on the insulator layer and facing a vacuum space, characterizedin that said insulator layer is made of an amorphous dielectricsubstance and has a film thickness of 50 nm or greater and has anamorphous phase with an average grain size of 5 to 100 nm as a majorcomponent and a polycrystal phase as a minor component, whereby theelectron emission device emits electrons when an electric field isapplied between the electron supply layer and the thin-film metalelectrode.
 2. An electron emission display device comprising:a pair offirst and second substrates facing each other with a vacuum space inbetween; a plurality of electron emission devices provided on the firstsubstrate; a collector electrode provided in the second substrate; and afluorescent layer formed on the collector electrode, each of theelectron emission devices comprising an electron supply layer of metalor semiconductor; an insulator layer formed on the electron supplylayer; and a thin-film metal electrode formed on the insulator layer andfacing a vacuum space, wherein said insulator layer is made of anamorphous dielectric substance and has a film thickness of 50 nm orgreater and has an amorphous phase with an average grain size of 5 to100 nm as a major component and a polycrystal phase as a minorcomponent.
 3. An electron emission display device comprising:a pair of adevice substrate and a transparent substrate facing each other with avacuum space in between; a plurality of ohmic electrodes formed inparallel on an inner surface of the device substrate; a plurality ofelectron emission devices provided on the ohmic electrodes, each of theelectron emission devices comprising an electron supply layer of metalor semiconductor; an insulator layer formed on the electron supplylayer; and a thin-film metal electrode formed on the insulator layer andfacing the vacuum space, wherein said insulator layer is made of anamorphous dielectric substance and has a film thickness of 50 nm orgreater and has an amorphous phase with an average grain size of 5 to100 nm as a major component and a polycrystal phase as a minorcomponent; a plurality of bus electrodes formed on parts of thethin-film metal electrodes and extending in parallel to one another andperpendicular to the ohmic electrodes so as to electrically connectadjoining thin-film metal electrodes; a plurality of collectorelectrodes provided in the transparent substrate; and fluorescent layersformed on the collector electrodes.
 4. An electron emission displaydevice according to claim further comprising a second auxiliaryinsulator layer with openings formed to separate the surfaces of thethin-film metal electrodes into a plurality of electron emissionregions.
 5. An electron emission display device according to claimwherein the second auxiliary insulator layer covers the bus electrodes.